How does a seismograph record seismic-waves?

Answer 1

Well you know when you write a sentence, the paper stays in one place while your hand moves the pen. But in a seismograph, it's the pen that remains stationary while the paper moves. Why is this? All seismographs make use of a basic principle of physics: Whether it is moving or at rest, every object resists any change to its motion. A seismograph's heavy weight resists motion during a quake. But the rest of the seismograph is anchored to the ground and vibrates when seismic waves arrive.